[PATCH] D61075: [CodeGenPrepare] limit overflow intrinsic matching to a single basic block

[Sanjay Patel via Phabricator via llvm-commits]

spatel marked an inline comment as done.
spatel added inline comments.


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Comment at: llvm/lib/CodeGen/CodeGenPrepare.cpp:1206
+  Instruction *InsertPt = nullptr;
+  for (Instruction &Iter : *Cmp->getParent()) {
+    if (&Iter == BO || &Iter == Cmp) {
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hfinkel wrote:
> If the DT was expensive, I'd actually suspect it was this scanning that made it so on large blocks. Does this happen multiple times such that a OBB cache would help?
I only have 1 test case to play with (I'll try to attach it to this review for reference), and it doesn't have large blocks. It's a ~66K line function with ~6K blocks.

>From what I can tell, the problem is that we reset the DT on any made change up at line 472. That seems like overkill, but I don't have the motivation to sort out which of the transforms in the loop could bypass that reset. 


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